Latch assembly

ABSTRACT

A top latch assembly for an emergency-exit door lock including a latch unit for mounting on the inner face of a door and having a pivotally supported latch bolt and a strike for mounting on the door frame and engageable with the latch bolt to shift the bolt toward latched position during closing movement of the door. Rigid and resilient parts of the latch bolt cooperate to grippingly engage an associated portion of the strike therebetween when the latch unit is in a latched position. The latch unit includes a reciprocably movable slide which cooperates with the latch bolt to retain it in a deadlocked position when the door is closed. When the door is open the latch bolt retains the slide in a hold-back position.

United States Patent 1 Balducci LATCH ASSEMBLY [75] Inventor: Walter 0. Balducci, New Britain,

Conn.

[73] Assignee: Emhart Corporation, Bloomfield,

Conn.

[22] Filed: June 4, 1971 [21] Appl. No.: 150,023

[52] 11.8. CI 292/92, 292/216, 292/333 [51] Int. Cl. E056 3/26 [58] Field of Search 292/333, 336, 216,

292/DIG. 71, DIG. 56, DIG. 73, 15, 51, 18, 21, 231, 78, 79, 76, 91, 92

[4 1 Dec.4,1973

1,203,116 10/1916 Hurd 292/21 Primary ExaminerRichard E. Moore Attorney-McCormick, Paulding & l-luber [5 7 ABSTRACT A top latch assembly for an emergency-exit door lock including a latch unit for mounting on the inner face of a door and having a pivotally supported latch bolt and a strike for mounting on the door frame and engageable with the latch bolt to shift the bolt toward latched position during closing movement of the door. Rigid and resilient parts of the latch bolt cooperate to grippingly engage an associated portion of the strike therebetween when the latch unit is in a latched position. The latch unit includes a reciprocably movable slide which cooperates with the latch bolt to retain it in a deadlocked position when the door is closed. When the door is open the latch bolt retains the slide in a hold-back position.

19 Claims, 6 Drawing Figures PATENTEUBEE 4W 3,776,582

SHEET 1 [if 2 [.JVENTOR. WALTER O. BALDUCCI I ATTORNEYS LATCH ASSEMBLY BACKGROUND OF INVENTION This invention relates in general to latch assemblies and deals more particularly with an improved deadlocking latch assembly for surface mounting on a door or the like. The latch assembly of the present invention may be employed in various environments but is particularly adapted for use with an emergency-exit door lock of the vertical rod type. Such a door lock generally includes a top and bottom latch assembly simultaneously released or unlatched by an intermediate panic bar actuated operating mechanism operably connected to the latch units by vertically disposed rods positioned adjacent the inner face of the door. A typical emergency-exit door lock of the aforedescribed type is illustrated and described in US. Pat. No. 3,324,692 to Welch, issued June 13, 1967, entitled Door Lock, and assigned to the assignee of the present application.

The latch assembly of the present invention is particularly adapted for use as an upper or top latch mechanism for an emergency-exit door lock and includes improved deadlocking and hold-back features.

SUMMARY OF THE INVENTION In accordance with the present invention an improved latch assembly is provided which includes a latch unit supporting a latch bolt and for mounting on the surface of a door and a strike for mounting on the door frame in the path of the latch bolt to engage the latch bolt and shift it toward latched position during closing movement of the door. The latch bolt has a rigid part and a resilient part which cooperate to grippingly engage an associated portion of the stroke in latched condition. The latch unit also includes a blocking member for connection to an associated operated mechanism and for deadlocking the latch bolt when the door is closed. When the door is open and the latch bolt is in an unlatched position the latch bolt cooperates with the blocking member to retain it in a hold-back position.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary side elevational view of a latch assembly embodying the present invention shown mounted on a door, the cover of the latch unit being shown in vertical section.

FIG. 2 is a fragmentary front elevational view of the latch assembly of FIG. 1, the cover being shown in vertical section.

FIG. 3 is a sectional view taken along the line33 of FIG. 2.

FIG. 4 is generally similar to FIG. 1 but shows the door in a partially open position and the latch bolt in a released position.

FIG. 5 is a sectional view taken generally along the line 55 of FIG. 2.

FIG. 6 is a perspective view of the latch bolt.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention is illustrated with reference to a top latch assembly for an emergency-exit door lock of the vertical surface rod type which includes an operating mechanism (not shown) for mounting on the inner face of a door and which may also include a bottom latch assembly. The top latch assembly includes a latch unit supporting a latch bolt and adapted to be mounted on the inner face of the door near the upper edge thereof and an associated keeper or strike .adapted to be mounted on the door frame in the path movable blocking member or slide associated with the latch unit and connected to the operating mechanism moves to a blocking position when the door is closed and retains the latch bolt in a deadlocked position. The latch bolt, in turn, cooperates with the slide when the door is open to retain the slide in a hold-back position which corresponds to the bolt retracted position of an associated bottom latch unit (not shown) interconnected with the top latch unit by the operating mechanism.

Referring now to the drawing and particularly to FIGS. 1 and 2, a top latch assembly embodying the present invention and indicated generally by the reference numeral 10 includes a latch unit and a strike respectively generally indicated at 12 and 14. The latch unit 12 is shown mounted on the inner face of an outwardly opening emergency-exit door 16 near the upper edge thereof. The strike 14 is mounted on a door stop 18 which comprises a part of the door casing frame and engages marginal portions of the door 16 when it is in its closed position as it appears in FIGS. 1, 2 and 5.

The latch unit 12 includes a frame or backplate 20 which supports a pivoted latch bolt 22 and a vertically reciprocable blocking member or slide indicated generally at 24. The backplate has a vertically elongated base 26 adapted to be secured adjacent the surface of the door 16 by a fastener or sex screw 28, as shown in FIG. 5. Upper and lower projections 30 and 32 extend forwardly from the central portion of the base 26 to respectively support the latch bolt 22 and the slide 24 as will be hereinafter further described. A central aperture 33 is formed in the base between the upper and lower projections. The lower projection 32 has a bore 34 which extends horizontally therethrough and includes a pair of vertically disposed forwardly facing guide surfaces 36, 36 and a pair of vertically disposed transversely outwardly facing guide surfaces 38, 38 as shown in FIG. 3. The backplate also includes a generally horizontally disposed lip 36 which projects forwardly from the lower edge of the base 26.

In accordance with the present invention, the latch bolt 22 has a rigid part 40 and a resilient part 42 which cooperate to define a strike receiving cavity 44 therebetween. The rigid part has a generally arcuate configuration as viewed in side elevation and includes a pair of transversely spaced generally rearwardly extending legs 46, 46 which receive the upper projection 30 therebetween. A roll pin 48 extends transversely through the projection 30 and through the legs 46, 46 to support the latch bolt 22 for pivotal movement about a transversely extending axis and relative to the backplate 20. The lower end portion of the latch bolt 22 is bifurcated to receive a roller or follower 50 supported on a transversely extending axis by another roll pin 52. The resilient part 42 may take various forms but preferably and as shown it comprises a spring formed in a generally U-shape from a piece of spring wire, the free end portions of which are received in holes in the rigid part 40. Each end of the spring 42 is retained in an associated hole in the part 40 by a headless screw fastener 56 as shown in FIG. 1.

As previously noted the slide 24 is supported by the lower projection 32. It includes a vertically disposed front wall 58 and a pair of transversely spaced vertically disposed side walls 60, 60 which extend rearwardly from the front wall 58 and straddle the lower projection 32 as clearly shown in FIG. 3. The side walls 60, 60 are joined together at their upper ends by a generally L-shaped portion 62 which has a narrow upwardly extending end adapted to be received between the legs 46, 46 and includes a forwardly facing abutment surface 64 for engaging the roller 50. A generally horizontally disposed cam surface 66 located between the side walls 60, 60 is inclined rearwardly and upwardly as best shown in FIG. 5. Another cam surface 68 which curves arcuately rearwardly and downwardly from the lower end of the surface 64 provides transition from the surface 64 to the cam surface 66. A transversely extending web 69 provides further connection between the legs 60, 60. The lower projection 32 extends through an opening in the front wall 58 defined by a pair of opposing slide surfaces 70, 70 which respectively engage the guide surfaces 38, 38, FIG. 3.

The slide 24 is retained in assembly with the back plate by a nylon spacer 76 received in the bore 34. This spacer has an annular flange 78 adapted for sliding engagement with the front wall 58. The latch unit 12 also includes a hollow cover 80 which surrounds the slide 24, a portion of the latch bolt 22 and bears against the spacer 76. A single sex screw 82 which passes through the cover 80, the spacer 78 and the bore 34 retains the cover in assembly with the door and the slide 24 in assembly with the back plate 20 and with an associated guide rod hereinafter described. It will be noted that the rearwardly facing peripheral surface of the cover 80 bears against the inner face of the door 16. An opening 84 is provided in the upper wall of the cover through which the latch bolt 22 operates. Referring to FIG. 2, it will be apparent that the back plate 20 is slightly wider than the latch bolt 22 so that the cover 80 cannot engage the latch bolt 22 even if assembled in a slightly misaligned condition. Another opening 86 is provided through the lower wall of the cover 80. In addition to retaining the slide, the flanged spacer 76 being slightly compressible also serves as a lock washer for retaining the cover 80 in assembled condition.

Further considering the strike 14, it includes a base 88 adapted for mounting on the door frame and provided with slotted apertures 90, 90 to facilitate adjustable fastening to the door frame. A rearwardly facing abutment surface 92 on the base 88 aids in locating the stroke 14 relative to the inner face of the door 16 when the strike is secured to the door stop 18. The strike 14 also includes a depending portion 93 which has a forwardly facing abutment surface 94 and a rearwardly facing abutment surface 96.

Connection between the slide 24 and an associated latch bolt operating mechanism (not shown) is provided by a threaded connector 98 received in the yoke 72 and connected thereto by a pin 100, the ends of which extend into the notches 74, 74. The lower end of the connector 98 is threadably received in an insert 102 which is, in turn, received in the upper end of a hollow vertical guide rod 104 disposed adjacent the surface of the door 16 and extending downwardly through the opening 86. The guide rod 104 is preferably cut to length in the field and assembled with and pinned to the insert 102 whereby the latch unit 10 may be assembled with the doors of various heights. The effective length of the rod 104 may be varied, as necessary, by rotating the connector 98 in a proper direction before it is assembled with the slide 24.

When the latch assembly 10 is mounted on a door, the stroke 14 is preferably first secured to the door frame with the abutment surface 92 thereof positioned generally adjacent the inner face of the closed door. Thereafter, the back plate 26 is positioned on the inner face of the door so that the stroke 14 is disposed in the path of the resilient part 42 when the door is open and the latch bolt is in its unlatched position substantially as shown in FIG. 4. The back plate is then secured to the door by the single sex screw 28. After the connector 98 is adjusted to conform to the distance between the operating mechanism and the lower end of the slide 24, the slide is positioned on the back plate 20 and the spacer 76 and cover are positioned and secured in assembly by the sex screw 82.

Considering now the operation of the latch assembly and referring particularly to FIGS. 1 and 5, when the door 16 is fully closed the slide 10 is in a lowered or blocking position as it appears in FIGS. 1, 2 and 5 so that the roller 50 engages the vertically disposed abutment surface 64 on the slide. Thus, the latch bolt 22 is deadlocked or restrained against pivotal movement by the slide 24. It will be further evident that the resilient part 42 exerts a biasing force against the rear abutment surface 96 to urge the rigid part into engagement with the abutment surface 94. In this manner the resilient part 42 cooperates with the rigid part 50 to grippingly engage the depending portion of the strike 14 therebetween. In this manner, the door is substantially restrained against vibration which might otherwise cause it to rattle. If adjustment is required to bring the marginal portion of the door 16 into engagement with the stop 18, such adjustment may be effected by repositioning the strike relative to the stop 18. When the door is opened as by the application of pressure to a panic bar or the like associated with an operating mechanism (not shown) mounted on the inner surface of the door, the operating mechanism causes the guide rod 104 to move upwardly thereby raising the slide 24 to its position in FIG. 4. Continuous pressure applied to the panic bar and the inner surface of the door causes the door to move toward an open position whereupon the latch bolt is pivoted toward its released position by the stroke 14. When the latch bolt 22 clears the stroke it continues to pivot under the influence of gravity and ultimately attains the position shown in FIG. 4. In the latter position, the roller is partially disposed in the opening 33 and generally tangent to the reverse slope of the surface 66. Thus, while the door remains open, the latch bolt 22 cooperates with the slide 24 to positively retain the slide in its raised or hold-back position. The upper latch unit may, if desired, be employed to retain an associated lower latch unit connected to the operating mechanism in a corresponding bolt retracted position, in a manner well known in the art, so that the latch bolt of the lower unit will not engage the floor surface during movement of the door. When the door is moved toward a closed position, the resilient member 42 engages the strike 14 which moves the latch bolt 22 towards its latched position. The arrangement of the cam surface 68 relative to the roller 50 prevents the slide 24 from moving to its fully lowered position until the latch bolt 22 is in a substantially fully latched position. The operating mechanism may, if desired, be arranged to apply a downwardly directed biasing force on the guide rod 104 so that the slide 24 will automatically move to its positive blocking position when the door is fully closed.

I claim:

1. In a door latch having a frame, a latch bolt supported by the frame for pivotal movement between a latching position and a releasing position, and a strike engageable with the latch bolt and operable to shift the latch bolt toward its latching position during closing movement of the door, the improvement wherein said latch bolt includes a rigid part and a resilient part secured in relatively fixed position to said rigid part for movement therewith and disposed in the path of said strike when said latch bolt is in its unlatched position, said resilient part being engageable with said strike during closing of the door to pivot said latch bolt toward its latching position, said rigid part and said resilient part defining a stroke receiving cavity therebetween'.

2. The combination set forth in claim 1 wherein said rigid part and said resilient part cooperate to grippingly engage an associated portion of said strike therebetween when said latch bolt is in said latched position.

3. The combination defined in claim 1 wherein said resilient part comprises a spring.

4. The combination as set forth in claim 1 including a blocking member supported on said frame and movable relative thereto between a blocking position and a hold-back position, said blocking member being movable in a direction away from said latch bolt to said blocking position when said latch bolt is in said latching position, said blocking member in said blocking position positively retaining said latch bolt in said latching position.

5. The combination as set forth in claim 4 wherein said latch bolt in its unlatched position retains said blocking member in said hold-back position whereby to positively restrain said blocking member against movement away from said latch bolt and toward said blocking position.

6. The combination as set forth in claim 4, wherein said door lock comprises a top latch assembly for an emergency-exit door lock, said blocking member is supported for vertically reciprocal movement relative to said frame, and said bolt is supported on said latch frame for pivotal movement about a horizontal axis and is freely movable to said unlatched position under the influence of gravity when said blocking member is in said hold-back position.

7. The combination as set forth in claim 4 wherein said blocking member comprises a slide supported for rectilinear sliding movement on said frame.

8. The combination as set forth in claim 4 wherein said latch bolt includes a roller follower and said blocking member has an abutment surface thereon, said follower engaging said abutment surface when said blocking member is in said blocking position.

9. A latch unit having a frame adapted to be mounted on the face of a door, a latch bolt supported for movement relative to said frame between latching and releasing positions, a blocking member supported on said frame for movement relative thereto between blocking and hold-back positions relative to said latch bolt, means associated with said blocking member for connecting said blocking member to an operating member, a cover adapted for cooperative engagement with the face of the door to provide substantial enclosure for said blocking member and said connecting means and partial enclosure for said latch bolt, and a single fastener for retaining said cover in cooperative engagement with the face of the door and said blocking member in assembled relation with said frame and said connecting means in connected relation with the operating member.

10. In a door latch having a frame, a latch bolt supported by the frame for pivotal movement between a latching position and a releasing position, and a stroke engageable with the latch bolt and operable to shift the latch bolt toward its latching position during closing movement of the door, the improvement wherein said latch bolt includes a rigid part and a resilient generally U-shaped wire spring member anchored on said rigid part and movable therewith and disposed in the path of said strike when said latch bolt is in its unlatched position, said spring member being engageable with said strike during closing of the door to pivot said latch bolt to its latching position, said rigid part and said spring member defining a strike receiving cavity therebetween.

11. A top latch assembly for a door vertically hinged to open outwardly relative to a door casing and comprising a strike for mounting on an upper portion of the door casing to depend therefrom, a top latch unit having a frame for mounting on the inner face of the door near the upper edge thereof and a latch bolt supported on said frame for pivotal movement about a horizontal axis between a latched position and a released position, said latch bolt having a part thereof engageable with said strike and cooperable therewith to move said latch bolt toward its latched position during closing movement of the door, said latch bolt having an upwardly opening strike receiving cavity therein for receiving and retaining said strike therein when said door is in its closed position and the latch bolt is in its latched position, said latch unit having a blocking member supported on said frame for vertical movement relative thereto between a blocking position and a hold-back position, said blocking member being movable downwardly and away from said latch bolt in moving from said hold-back position to said blocking position, said blocking member having a generally vertically disposed and inwardly facing abutment surface and a generally horizontally disposed downwardly facing first cam surface thereon, said abutment surface engaging said latch bolt when said latch bolt is in said latched position and said blocking member is in said blocking position to positively retain said latch bolt in its latched position, said latch bolt engaging said first cam surface when the door is in an open position and said blocking member is in its hold-back position to prevent movement of said blocking member toward its blocking position.

12. The combination as set forth in claim 11 wherein said first cam surface is upwardly and outwardly inclined in a direction away from said abutment surface.

13. The combination as set forth in claim 11 wherein said blocking member includes a second cam surface which provides a transition surface between said first cam surface and said abutment surface, said latch bolt engaging said second cam surface during movement of said latch bolt from its released to its latched position to prevent said blocking member from moving to its blocking position until said latch bolt attains its latched position.

14. The combination as set forth in claim 13 wherein said latch bolt includes a roller follower supported for rotation about a generally horizontally disposed axis, said roller follower engaging said blocking member.

15. The combination as set forth in claim 13 wherein said latch bolt has a rigid portion and a resilient portion, said part comprises a spring member mounted in a relatively fixed position on said rigid portion and defining said resilient portion, and said rigid portion and said spring member cooperate to define said stroke re ceiving cavity.

16. The combination defined in claim 11 including connecting means associated with said blocking member for releasably connecting said blocking member to an operating member, a cover adopted for cooperative engagement with the inner face of the door to provide a substantial enclosure for said blocking member and said connecting means and partial enclosure for said latch bolt, and a fastener for retaining said cover in cooperative engagement with the inner face of the door and said blocking member in assembled relation with said frame and said connecting means in connected relation with the operating member.

17. In a door latch having a frame, a latch bolt supported by the frame for movement between a latching position and a releasing position, and a strike engageable with the latch bolt and operable to shift the latch bolt toward its latching position during closing movement of the door, the improvement wherein said latch bolt includes a rigid part, a resilient part secured in relatively fixed position to said rigid part for movement therewith, said rigid part and said resilient part defining a strike receiving cavity therebetween, and a roller follower joumalled thereon, and said door latch includes a blocking member supported on said frame and movable relative thereto between a blocking position and a hold-back position, said blocking member having an abutment surface thereon and being movable in a direction away from said latch bolt to said blocking position when said latch bolt is in said latching position, said roller follower engaging said abutment surface when said blocking member is in said blocking position, said blocking member in said blocking position positively retaining said latch bolt in said latching position.

18. The combination as set forth in claim 17 wherein said blocking member has a first cam surface thereon, said follower engaging said cam surface when said lock member is in its unlatched position to positively retain said blocking member in said hold-back position.

19. The combination as set forth in claim 18 wherein said blocking member has a second cam surface thereon providing a transitional surface between said abutment surface and said first cam surface, said follower engaging said second cam surface during movement of said latch member from its released position to its latched position to prevent said blocking member from moving to said blocking position until said latch bolt has moved to said latched position.

UNITED STATES PATENT owner QERTEFIQATE I QQECTIGN Pa 3,776,582 Dated December 4, 1973 lnventofls) Walter O. Balducci It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 1, line 35, "stroke" should be --strike-.

Col. 3, line 54, "stroke" should be -strike--.

Col. line 12, "stroke" should be --strike--.

C01. line 49, "stroke" should be -,--strike-.

, line 22, "stroke" should be --strike--.

Col. 4, line 50, "stroke" shouldbe --strike-- Col. 5

, line 48, "bolt" should be deleted arid "latch bolt" substituted,

Col.

Col. 6, line 13, "stroke" ,should'be -strike- 001. 7, line 12, "stroke" should be --strike-.

Col. 8, line 18 and 19, "lock member" should be --latch bolt- Col. 8, line 19, "unlatched" should be --releasing--.

Signed and sealed this 23rd day of April 1971 (SEAL) Attest:

EDE'JAIZLJ PiJ-LrlTCHEl-LJEQ G. I-IARSHALL DAMN Attesting Officer Commissioner of Patents FORM PC4050 (169) uscoMM-Dc 60376-P59 V .5. GOVERNMENT PRINTING OFFICE 1 I969 3'G'33, 

1. In a door latch having a frame, a latch bolt supported by the frame for pivotal movement between a latching position and a releasing position, and a strike engageable with the latch bolt and operable to shift the latch bolt toward its latching position during closing movement of the door, the improvement wherein said latch bolt includes a rigid part and a resilient part secured in relatively fixed position to said rigid part for movement therewith and disposed in the path of said strike when said latch bolt is in its unlatched position, said resilient part being engageable with said strike during closing of the door to pivot said latch bolt towArd its latching position, said rigid part and said resilient part defining a stroke receiving cavity therebetween.
 2. The combination set forth in claim 1 wherein said rigid part and said resilient part cooperate to grippingly engage an associated portion of said strike therebetween when said latch bolt is in said latched position.
 3. The combination defined in claim 1 wherein said resilient part comprises a spring.
 4. The combination as set forth in claim 1 including a blocking member supported on said frame and movable relative thereto between a blocking position and a hold-back position, said blocking member being movable in a direction away from said latch bolt to said blocking position when said latch bolt is in said latching position, said blocking member in said blocking position positively retaining said latch bolt in said latching position.
 5. The combination as set forth in claim 4 wherein said latch bolt in its unlatched position retains said blocking member in said hold-back position whereby to positively restrain said blocking member against movement away from said latch bolt and toward said blocking position.
 6. The combination as set forth in claim 4, wherein said door lock comprises a top latch assembly for an emergency-exit door lock, said blocking member is supported for vertically reciprocal movement relative to said frame, and said bolt is supported on said latch frame for pivotal movement about a horizontal axis and is freely movable to said unlatched position under the influence of gravity when said blocking member is in said hold-back position.
 7. The combination as set forth in claim 4 wherein said blocking member comprises a slide supported for rectilinear sliding movement on said frame.
 8. The combination as set forth in claim 4 wherein said latch bolt includes a roller follower and said blocking member has an abutment surface thereon, said follower engaging said abutment surface when said blocking member is in said blocking position.
 9. A latch unit having a frame adapted to be mounted on the face of a door, a latch bolt supported for movement relative to said frame between latching and releasing positions, a blocking member supported on said frame for movement relative thereto between blocking and hold-back positions relative to said latch bolt, means associated with said blocking member for connecting said blocking member to an operating member, a cover adapted for cooperative engagement with the face of the door to provide substantial enclosure for said blocking member and said connecting means and partial enclosure for said latch bolt, and a single fastener for retaining said cover in cooperative engagement with the face of the door and said blocking member in assembled relation with said frame and said connecting means in connected relation with the operating member.
 10. In a door latch having a frame, a latch bolt supported by the frame for pivotal movement between a latching position and a releasing position, and a stroke engageable with the latch bolt and operable to shift the latch bolt toward its latching position during closing movement of the door, the improvement wherein said latch bolt includes a rigid part and a resilient generally U-shaped wire spring member anchored on said rigid part and movable therewith and disposed in the path of said strike when said latch bolt is in its unlatched position, said spring member being engageable with said strike during closing of the door to pivot said latch bolt to its latching position, said rigid part and said spring member defining a strike receiving cavity therebetween.
 11. A top latch assembly for a door vertically hinged to open outwardly relative to a door casing and comprising a strike for mounting on an upper portion of the door casing to depend therefrom, a top latch unit having a frame for mounting on the inner face of the door near the upper edge thereof and a latch bolt supported on said frame for pivotal movement about a horizontal axiS between a latched position and a released position, said latch bolt having a part thereof engageable with said strike and cooperable therewith to move said latch bolt toward its latched position during closing movement of the door, said latch bolt having an upwardly opening strike receiving cavity therein for receiving and retaining said strike therein when said door is in its closed position and the latch bolt is in its latched position, said latch unit having a blocking member supported on said frame for vertical movement relative thereto between a blocking position and a hold-back position, said blocking member being movable downwardly and away from said latch bolt in moving from said hold-back position to said blocking position, said blocking member having a generally vertically disposed and inwardly facing abutment surface and a generally horizontally disposed downwardly facing first cam surface thereon, said abutment surface engaging said latch bolt when said latch bolt is in said latched position and said blocking member is in said blocking position to positively retain said latch bolt in its latched position, said latch bolt engaging said first cam surface when the door is in an open position and said blocking member is in its hold-back position to prevent movement of said blocking member toward its blocking position.
 12. The combination as set forth in claim 11 wherein said first cam surface is upwardly and outwardly inclined in a direction away from said abutment surface.
 13. The combination as set forth in claim 11 wherein said blocking member includes a second cam surface which provides a transition surface between said first cam surface and said abutment surface, said latch bolt engaging said second cam surface during movement of said latch bolt from its released to its latched position to prevent said blocking member from moving to its blocking position until said latch bolt attains its latched position.
 14. The combination as set forth in claim 13 wherein said latch bolt includes a roller follower supported for rotation about a generally horizontally disposed axis, said roller follower engaging said blocking member.
 15. The combination as set forth in claim 13 wherein said latch bolt has a rigid portion and a resilient portion, said part comprises a spring member mounted in a relatively fixed position on said rigid portion and defining said resilient portion, and said rigid portion and said spring member cooperate to define said stroke receiving cavity.
 16. The combination defined in claim 11 including connecting means associated with said blocking member for releasably connecting said blocking member to an operating member, a cover adopted for cooperative engagement with the inner face of the door to provide a substantial enclosure for said blocking member and said connecting means and partial enclosure for said latch bolt, and a fastener for retaining said cover in cooperative engagement with the inner face of the door and said blocking member in assembled relation with said frame and said connecting means in connected relation with the operating member.
 17. In a door latch having a frame, a latch bolt supported by the frame for movement between a latching position and a releasing position, and a strike engageable with the latch bolt and operable to shift the latch bolt toward its latching position during closing movement of the door, the improvement wherein said latch bolt includes a rigid part, a resilient part secured in relatively fixed position to said rigid part for movement therewith, said rigid part and said resilient part defining a strike receiving cavity therebetween, and a roller follower journalled thereon, and said door latch includes a blocking member supported on said frame and movable relative thereto between a blocking position and a hold-back position, said blocking member having an abutment surface thereon and being movable in a direction away from said latch bolt to said blocking position when said latch bolt is in saId latching position, said roller follower engaging said abutment surface when said blocking member is in said blocking position, said blocking member in said blocking position positively retaining said latch bolt in said latching position.
 18. The combination as set forth in claim 17 wherein said blocking member has a first cam surface thereon, said follower engaging said cam surface when said lock member is in its unlatched position to positively retain said blocking member in said hold-back position.
 19. The combination as set forth in claim 18 wherein said blocking member has a second cam surface thereon providing a transitional surface between said abutment surface and said first cam surface, said follower engaging said second cam surface during movement of said latch member from its released position to its latched position to prevent said blocking member from moving to said blocking position until said latch bolt has moved to said latched position. 